The present application claims priority under 35 USC 119 to Japanese Patent Application Nos. 2001-109122 filed on Apr. 6, 2001 2001-156749 filed on May 25, 2001 and 2001-272693 filed on Sep. 7, 2001 the entire contents thereof are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a steering damper system for a motorcycle for damping a swing of the handle during operation, and more particularly to a steering damper system that can vary the damping force.
2. Description of Background Art
Steering damper systems for generating a damping force to prevent the swing of the handle due to a kick-back at the time of a disturbance or the like, have been known (one example is Japanese Patent No. 2593461). In addition, technologies in which a damping force is variable so that the damping force is generated only when it is needed and that needless damping forces are not generated in other situations are also known. For example, a technology is known in which the damping force is controlled based on a steering angle and operating velocity (Japanese Patent Laid-open No. Sho 63-64888). In addition, a technology is known in which the damping force is controlled based on variations in front-wheel load (Japanese Patent Publication No. Hei 7-74023).
According to the damping force control methods of the prior-art examples, it is impossible to discriminate whether the cause generating a swing of the handle is an external cause such as a disturbance or an intentional operation caused by the rider. Therefore, even when the rider intentionally operates the handle during cornering, a damping force might be generated if a predetermined condition is established, whereby the handle load would be enlarged. Accordingly, the most preferable thing as a steering damper system is to generate the damping force only upon an unintentional cause such as a disturbance and not to generate the damping force in other situations.
However, even including the above prior-art examples, a steering damper system does not exist which enables a control according to the contents of the handle operation. It is desired to perform such a control that an appropriate damping force can be obtained according to the contents of the handle operation. Further, it is considered that if the damping force is varied according to variations in vehicle velocity or vehicle acceleration, it is possible to generate a damping force suitable for the active will of the rider. Accordingly, it is an object of the present invention to realize a steering damper system which can generate a damping force suitable for the active will of the rider.
In order to solve the above-mentioned problems, a first aspect of the invention pertaining to the steering damper system of the present application includes a steering damper system for exerting a damping force on a turning action of a front wheel steering system supported at a front portion of a vehicle body. With the damping force being variable, a rotational angular velocity of the steering system is generated by an unintentionally caused turning action and a moment is intentionally exerted on the steering system in the opposite direction so as to restrain and measure the unintentional turning action. The damping force of the steering damper is eliminated or reduced when the load direction of the moment and the turning direction of the steering system are in the same direction.
At this time, while the damping force of the steering damper is eliminated or reduced when the direction of the moment and the turning direction of the steering system are in the same direction, a damping force may be generated or increased in the steering damper when the direction of the moment and the turning direction of the steering system are in opposite directions. Further, a damping force may be generated in the steering damper when the rotational angular velocity has exceeded a predetermined threshold value.
In addition, a damping force may be generated in the steering damper when the direction of the moment and the turning direction of the steering system are in opposite directions and the load of the moment has exceeded a predetermined threshold value. Furthermore, in the controls where the direction of the moment and the turning direction of the steering system are in the same direction or in opposite directions, a condition wherein the rotational angle exceeds a predetermined threshold value may be added to the control conditions.
A second aspect of the invention includes a steering damper system for exerting a damping force on a turning action of a front wheel steering system supported at a front portion of a vehicle body. With the damping force being variable by a damping force variable means, the damping force variable means varies the magnitude of the damping force through a multistage changeover according to the vehicle velocity, vehicle acceleration or both the vehicle velocity and vehicle acceleration.
According to the present invention, a control means for operating the damping force variable means is provided wherein the control means changes over the damping force variable means in a multistage manner according to a plurality of predetermined velocity threshold values concerning the vehicle velocity or a plurality of predetermined acceleration threshold values concerning the vehicle acceleration. The acceleration threshold values include a function of the vehicle velocity which decreases as the vehicle velocity increases. Furthermore, a constitution may be adopted in which the damping force variable means is fixed in a predetermined changeover position within the multistage changeover range when a changeover of the damping force cannot be achieved notwithstanding a condition for changing over the damping force is present.
The steering damper system according to the first aspect of the present invention performs a control based on the moment exerted on the handle and the rotational angular velocity. Therefore, when the direction of the moment and the turning direction of the handle are in the same direction, for example, when the rider performs an intentional turning operation on the handle at the time of cornering, the direction of the moment exerted on the handle and the turning direction of the steering system coincide with each other. This results in the detection wherein the current operation is an intentional handle operation by the ride. As a result, the damping force is eliminated or reduced, irrespective of the magnitude of the moment and the rotational angular velocity. Therefore, the damping force is not generated or is reduced upon the rider""s intentional handle operations at the time of stopping, managing or running the motorcycle or the like situations, whereby a light handle operation is realized. Moreover, it is possible to restrain the generation of needless damping forces, according to the handle operation conditions.
In addition, the damping force can be generated or increased only when the moment and the turning direction of the steering system are in opposite directions. For example, when a turning action is generated in the steering system due to a disturbance from the road surface at the time of operation, the turning direction of the steering system and the direction of the moment exerted on the steering system by the rider so as to restrain the turning action are different. Therefore, it is detected that the current action of the steering system is an unintentional action, and a damping force is generated or increased in the steering damper. As a result, the turning action of the steering system due to the disturbance from the road surface or the like can be restrained. Therefore, there is realized a steering damper system which can restrain the turning of the steering system by the damping force only when it is needed, according to the actual conditions at the time of operation and which can generate an appropriate damping force without being against the active will of the rider.
Further, when a predetermined threshold value is set concerning the rotational angular velocity and a damping force is generated or increased in the steering damper only when the threshold value has been exceeded, the steering damper can be made to function selectively only to such an excessive disturbance of disturbances from the road surface that might lead to kick-back, and, as a result, the generation of needless damping forces can be restrained more securely.
When a condition wherein the load of the moment exceeds a threshold value is added to the condition for the control in the case where the direction of the moment and the turning direction of the steering system are opposite, a further appropriate control is realized. The same result can be obtained also when a condition that the rotational angle exceeds a predetermined threshold value is added to the conditions for the controls in the case where the direction of the moment and the turning direction of the steering system are the same or opposite.
The second aspect of the invention resides wherein the damping force variable means varies the magnitude of the damping force in a multistage manner according to vehicle velocity, vehicle acceleration or both of vehicle velocity and vehicle acceleration. Therefore, a damping force of a required magnitude can be appropriately given to the steering damper in response to a required running condition, in relation to the vehicle velocity and the vehicle acceleration, and, therefore, there is realized a steering damper system which can generate an appropriate damping force without being against the active will of the rider.
Generally, when the vehicle velocity is low, the vehicle acceleration is high and, therefore, kickback would easily occur. In view of this, when a control device for changing over the damping force variable means is set so as to perform a control in a multistage manner according to a pluralities of predetermined velocity threshold values or acceleration threshold values, it is possible to obtain an appropriate damping force according to the vehicle velocity or the vehicle acceleration.
In this case, when an acceleration threshold value is made to be a function of vehicle velocity which decreases as the vehicle velocity increases and the damping force is controlled based on the acceleration threshold value, the acceleration threshold value is higher on the lower-velocity side. Therefore, a large damping force can be generated only when the vehicle acceleration is great as compared to the vehicle velocity in a comparatively lower velocity region. Therefore, an appropriate damping force based on the correlation between vehicle velocity and vehicle acceleration can be generated to prevent kick-back, according to the actual situations of a motorcycle such that a large vehicle acceleration is generated at the time of low vehicle velocity, to reduce the front-wheel load, leading to a result wherein the kick-back would easily occur.
Furthermore, when the damping force variable means cannot change over the damping force notwithstanding a condition when the changing over of the damping force is present, the changeover position is fixed in a predetermined region within a changeover range that is varied in a multistage manner, so that a predetermined damping force can be generated even in such a situation.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.